Growth hormone is DNA recombinant human growth hormone, which has the same effect as human growth hormone. Can promote bone, internal organs and body growth. Promote protein synthesis, affect fat and mineral metabolism, and play a key role in human growth and development. Approximately 80% of the subcutaneous injection is absorbed, the blood concentration peaks within 5 hours, and the half-life is 4 hours. 90% of the injected dose is metabolized in the liver, and only about 0.1% is excreted in the original form by the biliary tract and kidneys.
Figure 1. Protein structure of growth hormone.
The general term for all kinds of hormones that can regulate and control the endocrine mechanism of animals, so that the nutrients entering the body can be redistributed in a beneficial direction according to human growth requirements for animals. Hormones only regulate (increase or decrease) the speed of certain physiological reactions, but they cannot provide the energy of the reaction process itself, nor can they start new metabolic reactions. Therefore, when the original response is excessively stimulated, it is as harmful as when the hormone is deficient.
Insulin-like growth factor 1 (IGF-1)
Insulin-like growth factor 1 (IGF-1) is also known as the somatostin C, which Is a protein encoded by the human gene IGF-1. IGF-1 is the major mediator of growth hormone (GH) action. Growth hormone is produced in the anterior pituitary gland, is released into the bloodstream, and then stimulates the liver to produce IGF-1. Then, IGF-1 stimulates the growth of the whole body and has the effect of promoting growth on almost all cells in the body (especially skeletal muscle, cartilage, bone, liver, kidney, nerve, skin, hematopoietic and lung cells). In addition to insulin-like effects, IGF-1 can also regulate cellular DNA synthesis.
Figure 2. Protein structure of insulin-like growth factor 1 (IGF-1).
The main function of IGF-1 is mediated by binding to its specific receptor, IGF1R, which is present on the surface of many cell types in many tissues. Combining with IGF1R initiates intracellular signaling. IGF-1 is one of the most effective natural activators in the AKT signaling pathway, a stimulator of cell growth and proliferation, and an effective inhibitor of programmed cell death. The IGF-1 receptor appears to be a "physiological" receptor because it binds IGF-1 with a significantly higher affinity than the insulin receptor. Insulin-like growth factor 1 receptor (IGF-1R) and other tyrosine kinase growth factor receptors signal through multiple pathways. The key pathway is regulated by phosphatidylinositol 3 kinase (PI3K) and its downstream partner, the mammalian target (mTOR) of rapamycin.
Figure 3. 3D model of IGF-1.
Under the stimulation and control of the hypothalamus factor GH releasing hormone (GHRH), growth-promoting cells in the anterior pituitary gland secrete growth hormone (GH). GH works directly or indirectly through insulin-like growth factor 1 (IGF-1). GH and IGF together promote mammalian growth and affect the regulation of metabolism. In addition, the GH/IGF-1 axis has been shown to actively regulate the lifespan of worms, fruit flies, and mice. However, whether the GH/IGF-1 axis has an equal effect on human lifespan remains to be determined. Human GH secretion gradually decreases with age, while IGF-1 levels decrease. GH/IGF-1 has an effective effect on the central nervous system, regulating plasticity and function. Age-related GH/IFF-1 depletion is associated with increased susceptibility to the development of cognitive and sleep disorders.
Jansen M.; et al. Sequence of cDNA encoding human insulin-like growth factor I precursor. Nature. 1983, 306 (5943): 609-11.